Heat exchanger apparatus



June 30, 1959 w, 3, CANTERBURY 2,892,617

HEAT EXCHANGER APPARATUS Filed Feb. 4, 1957 3 Sheets-Sheet l INVENTOR. Mamas .0 (hum-25am uiftom ys June 1959 w. D. CANTERBURY HEAT EXCHANGER APPARATUS 3 Sheets-Sheet 2 Filed Feb. 4, 1957 w R mw wp m w Wf/ NM 0 1a a June 30, 1959 w. D. CANTERBURY HEAT EXCHANGER APPARATUS 3 Sheets-Sheet 3 Filed Feb. 4, 1957 m A D E T A E H INVENTOR.

w w 5 2 W w a w 0- w a m fl Wm 4 United States Patent HEAT EXCHAN GER APPARATUS Wallace D. Canterbury, Gardena, Calif., assignor to US. Industries, Inc., a corporation of Delaware Application February 4, 1957, Serial No. 637,985

19 Claims. (Cl. 257-202) The present invention relates generally to heat exchangers and more particularly to heat exchanger apparatus utilizing air as a medium for changing the temperature of a liquid.

In the United States Letters Patent No. 2,279,941, issued January 10, 1956, to H. E. Rose et al., there is shown a fluid actuated pumping jack which is especially adapted for use in pumping oil from an oil well. This fluid actuated pumping jack employs a vertically extending hydraulic cylinder and a piston slidably disposed therein. The piston is attached to the upper end of a sucker rod string, and it is raised in the cylinder by pressurized hydraulic liquid. A reservoir tank is provided for this hydraulic liquid, the liquid being pumped by a rotary pump from the reservoir tank to the lower end of the cylinder below the piston during a power stroke of the latters piston. The hydraulic liquid is returned to the reservoir tank during the downward movement of the piston under the weight of the sucker rod string. During operation of this pumping jack, the temperature of the hydraulic liquid is often raised to the point that cavitation takes place within the rotary pump. Such cavitation not only reduces the efiiciency of the unit but also results in extremely noisy operation. This noisy operation prohibits the use of these hydraulic pumping jack units near residential areas. The preferred form of heat exchanger apparatus embodying the present invention was especially adapted for use with the aforedescribed pumping jack and when employed therewith is capable of maintaining the temperature of the hydraulic liquid sufiiciently low that cavitation of the rotary pump does not occur.

It is a major object of the present invention to provide novel and improved heat exchanger apparatus.

Another object is to provide heat exchanger apparatus that utilizes high velocity air as a temperature-changing medium for a liquid, it having been determined that the rate at which an exchange of heat through a wall takes place is a function of the velocity of the fluids disposed on either side of the wall.

A further object of the invention is to provide heat exchanger apparatus that is compact in size and light in weight.

Yet another object of the invention is to provide heat exchanger apparatus of the aforedescribed nature which is inexpensive to construct and maintain as compared to heretofore-proposed heat exchangers.

It is a further object of the invention to provide heat exchanger apparatus which is extremely eflicient in operation whereby it affords a maximum temperature changing capacity with a minimum consumption of power.

An additional object is to provide heat exchanger apparatus especially adapted for use with a liquid-containing tank and wherein high velocity air is forced through the interior of this tank and thereafter is expelled over the tanks exterior.

Another object is to provide heat exchanger apparatus incorporating a liquid-containing tank and a belt-driven blower, the blower being slidably mounted relative to the cooling a liquid but which can readily be adapted to heat a liquid.

These and other objects and advantages of the present invention will become apparent from the following detailed description, when taken in conjunction with the appended drawings wherein:

Figure 1 is a perspective view of a preferred form of heat exchanger apparatus embodying the present invention;

Figure 2 is a fragmentary side elevational view of the blower end of said apparatus;

Figure 3 is a vertical sectional view taken on line 33 of Figure 2;

Figure 4 is a vertical sectional view taken on line 44 of Figure 3;

Figure 5 is a horizontal sectional view taken on line 55 of Figure 4;

Figure 6 is a vertical sectional view taken on line 6-6 of Figure 4;

Figure 7 is a perspective view of a modified form of said heat exchanger apparatus; and

Figure 8 is a fragmentary side elevational view of said modified form.

apparatus embodying the present invention includes a reservoir tank T for a quantity of hydraulic liquid 10, an air blower B mounted at one end of the reservoir tank T and having its discharge connected to main duct means M extending through the interior of the tank T. The ends of the main duct means M opposite the blower B are in communication with return duct means R. A conventional pump P is mounted upon the reservoir tank T. This pump P and the blower B are driven by an electric motor E, the latter also being mounted upon the tank T. In operation, the pump P will draw hydraulic P is connected to a pressure line 12 shown in Figure 1.

The hydraulic liquid 10 will be withdrawn from the interior of the reservoir tank T through an inlet conduit 14, the upper end of which is connected to the intake of v the pump P. The hydraulic liquid will be returned to the interior of the reservoir tank T by a return line 16. The returned hydraulic liquid flowing through the reservoir tank T will be cooled by air forced through the main duct means M and the return duct means R by the blower B. The return duct means R are curved so as to direct the air which has passed through the main duct means M over the exterior of the tank T.

More particularly, the reservoir tank T is generally cylindrical in configuration, and may conveniently be of welded steel construction. Its lower portion is atfixed to a pair of brackets 20 and 21. These brackets are in turn secured to a suitable base 22. The main duct means M extends longitudinally through the interior of the tank T and, as shown in Figures 4 and 5, include an entrance portion 24 disposed proximate the discharge of the Patented June 30, 1959 rectangular in cross-section. The leg portions are parallel"and"ex ten'd' through oneend wall" 38 of the tank T, as shown In Figures 4 and 5.. The return duct means R cons ist of a pair of identical difi user members .32.and

34; The inlet end 360i diffuser niember 3 2 -is .affixed to tliejendjof leg portion 281 remote from the blower BL tnallyi f eta k n .8. whileihe n et q d.

of thlegother' difiuser member34 isiaflixed to the same end .o f leg' portion.30. 'The outlet' ends 40 of .th e dife fuser 1 members 7 are open and face the opposite external a frarnework 46... A shroud .47.encloses the rotor 41 an d is aflixed to the framework. 46.1 This framework. 46 includes a p air of parallel, horizontal rail elements 50 and 52. As' s'liownin'Figurel, the rail elements 50 52 are each .proyided.wit h a pair. of longitudinallyspaced elongated slots 54. These slots 54 receive mounting bolts 56 which. are attached to theopposite sides of the'reservoir tankT so as to secure the: rails Stland 52 thereto. This arrangement permits longitudinal adjustment of the blower framework 46 towards and away frorn the endwallof the tank T. for a purpose to be set forth hereinafterl' It shouldbe particularly noted that the discharge portion 158 of the blower shroud 47; is rectahgular in configuration, and as indicated in Figures 4 and 5, it telescopicallyinterfits within the entrance-portior 24s of. the mainiduct means M. A driven sheave sfi'is keyed to one side ofthe rotor shaft 42, as is shown in FiguresZ and 4. i A I I K 7 V ,'The' pump P is also of conventional construction and in practicefafgear pump hasv proven satistfactory. The

lower; portion of this pump P is aflixed to a mounting bracket 60 welded to the upper portion of the .reservoir tank'TJ The shaft62 of the pump is keyed to a blower.

drive sheavef64 This blower drive sheave 64 is connected by. abelt .66. to the drivenysheave.59 that is keyed to fthej shaft 42 of the blower B. A second;sheave 68;

iskeyed. to the pump shaft v62 adjacent the aforementioned blower; drive sheave 64. This latter sheave 68 is connectedby a belt.70 .to a driving sheave 72 that is keyed to shaft of theelectric motor E. i

As shown in Figures 4, and 6, the intake. of the v pumpjis in communicationwith the lower portionof the tank; T by. the inletconduit 14. Preferably, the lower; end' of this. inlet conduit 14 will be proyided with a.

conventionallfilter 74. In practice, a wire mesh filter haspr'ov'en satisfactory. The upper, portion of the inlet conduit 14 extends .througha cap 76 that is bolted to a cylindrical neck'78 formed on the upper portion o t-the T. A conventional oil breather 80 is al soafiixed; tothiscap 76., Referring now to Figure l the discharge of the pump P is connected tothepressure line 12. Preferably, a conventional check valve 82 will be inter passed. n. i p ss r n o stream f. h s

chccklvalye 82. a conventional pressure relief valve unit, 84;. is. positioned. With. this arrangement should the pressure withinthe, pressure line 12 riseabove a pre-.

determined value. a portion; of the. hydraulic liquid flow ing th r'ou'gh theline wiu'be returned to .th inter oror the tank T' through .a. by-pass pipe 86.

As shown particularly inFigureA the end of the-returnsline 16 adjacent the reservoir. tank T. includesa threaded fittingfitl,centrallyafligred to the upper portion of the tank' end wall 36. Thedopp osite end'of this r ade tt n flixed .t ischa e b rsetu e. x end .-dowm ard nd anai.-

ia l eii n h an fldwallfi e- Tremor. portion of hydraulic liquid returned through the discharge tube follows the path indicated by the directional arrowsin Figures 4 and 5. It should be observed that this path is counter to the direction of flow of the cooling air being forced through the main duct means M. To obtain such flow the interior of the tank T is provided with a horizontal floor 92 which interconnects the lower portion of the leg portions 2 8; and 30 of the main duct means M. One end of this floor is afixed to the tank end wall 38cwhilethecother is bent upwardlyladjacent the filte r 74 so asto form an upstanding battle .94. This baflle has a. height corresponding to that of the leg portions 28"a'nd 30 "of the main duct means M. With' this arrangement, theimajorport-ionofi the returned hydraulic liquid discharged fromthedischarge tube 90 will tend to flow longitudinally relative to the reservoir tank T towards the blower end of the tank T between the facing sides of the leg portions 28 and 30 until it reaches the baiile 94. The presence of this bafile 94 will ,cause this hydraulic liquid to flow over the top ofthe. battle and also over thetop. of the leg portions 28. and iall,- as,indi-. cated'by the directional arrows in Figures3, 4. and6. Thereafter, this hydraulic liquid may enter theinlet conduit 14 by means of the vfilter 74.

Inthe operation of the aforeclescribed preferredembodiment of the present invention. rotation of the. elec; trio motor E .willbe transferrecl.to the sheave,68 of the. pump R-by belt 70. Rotation of the sheave 68 will in turn ffect concurrent rotation of the blower drive sheave 64. Rotationofnthis latter sheave. 64.will be transferred to the driven sheave 59,015 the blower B by the belt 66.. As shownparticularly in Figure 5, thepressurized air from thebldwer B .willenterthe entrance'portion 24o? the main "duct means M through the blowers discharge portion 58. Inasmuch asthe combined vertical cross-sec} tionala'reaot' the leg portionslii and3ll is less .thar that. of the entrance portion 24, 'as notedhereinabove, the air. flowing from. the: entrance portion into th e' leg portions. will undergo anIinc'rease in".velocity.. Such increase fin velocity. will bejproportional to the comparative, vertical crossrfsefctional areas of these members. This increa se in velocityof, theair flowing to the legportions. 28 .and 3liwill serve to increase the, rate ot heat exchange through. the walls defining theleg portions. After this highve locity cooling air haspass'edthroughthe leg po rtions 28 and 30, it 'will flow through. the ditfuser. membersBZ I and i34 These difiuser members will seryeto reverse theldirectionof flow of this. cooling air and directit over the opposite external sidesoi the reservoir tank T. The difiuser membersI32and34 should be. sodesigned as to provide minimum diffusion of. this air as it flows. over the external surtaces of thereservoir-tank In thismanner, ajmarimurnheatergchange between the airand the hydraulic liquidwithinthe. reservoir tank willbe attained The returned.hydraulic liquid l0 ,will enter the reservoir tank T: througl rthe return line .16. and the attached discharge tube 90. Upon leaving-the discharge-tube90, this liquidwill flow. away from the -tank end waliQS in a generaliy. longitudinal. direction relative to the, reservoir tank T towards the blower end of the tank, as noted hereinbefore. Referring now to Figures 3 and 6, the volume of. hydraulic liquid 10 within,the reservoir tank shouldbe so maintainedthat the level on the outer sides, of the leg portions 28, and Sllis lower; than. the heightv ofthese leg po rtions and that of the baifie 94. With this arrangement, the hydraulic fiuid contained between the facing surfacesof these leg portions, the tank; .end wall 38. and thebaflieS-iwill be forcedtoflow over: the upper surfaces of the leg portions. An air breakout platform isthereby defined-along the upper surfaces ofthe ngmnmngzs, and 3t) lnthis regard, the .iilm o f hy-. draulic liquid 'ov erflowing. the top surfaces of fthese leg portions is comparatively" thin. As this hot hydraulic? liquid comes into contact with the uppersurtaces-of,the. st srt qa a he .sarte s. ssisn. t s? r; bbl s .611- traiiiedin the hydraulic liquid is increased because of their reduction in volume resulting from the cooling action afforded by these upper surfaces. Accordingly, these air bubbles will burst and release their air into the space above the level of the hydraulic liquid. Thus, the cooled hydraulic liquid entering the intake of the pump P will not produce cavitation. The air released during the collapse of these air bubbles will leave the upper portion of the reservoir tank T by means of the oil breather 80.

As noted hereinabove, the longitudinal spacing of the blower B relative to the adjacent end of the reservoir tank T may be adjusted by means of the slots 54 and mounting bolts 56. During such longitudinal blower adjustment the shrouds discharge portion 58 will slide within the entrance portion 24 of the main duct means M. With this arrangement, it is possible to move the blower B towards and away from the splitter 31 until the static head atfording maximum air delivery with minimum power expenditure is obtained. This longitudinal adjustment provision also makes it possible to adjust the tightness of the belt 66.

Referring now to Figures 7 and 8, there is shown a modified form of the heat exchanger apparatus embodying the present invention. This modified form is adapted for use where it is desired to heat the hydraulic liquid within the reservoir tank T rather than cool such liquid. In order to effect such heating, the blower B of the aforedescribed heat exchanger apparatus is merely enclosed within a two piece housing 100 having communication with a source of heated fluid, such as the interior of the hood 102 of an internal combustion engine 104. With this arrangement, as shown clearly in Figure 8, atmospheric air entering the interior of the hood 102 through its louvers 106 will be drawn over the external surface of the internal combustion engine 104 so as to be raised in temperature. This heated air will then be drawn through the housing 100 into the intake of the blower B. The blower B will force this air through the main duct means M and the return duct means R of the reservoir tank T in the manner described hereinabove so as to effect heating of the hydraulic liquid flowing therethrough. The housing 100 is formed of two telescopically interfitting sections 100a and 10012. This arrangement makes it possible to readily adjust the spacing between the engine 102 and the blower B to the space requirements of the installation. Preferably, the interior of both housing sections will be provided with a thermal insulat ing medium (not shown).

It will be apparent to those skilled in the art that various modifications and changes may be made with respect to the foregoing detailed description without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. Heat exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank in heattransfer relationship with the liquid contents of said tank; blower means connected with the inlet end of said main duct means so as to urge fluid through the latter in a first direction; and return duct means in communication with the outlet end of said main duct means, said return duct means extending externally of said tank and being curved so as to direct said fluid over the exterior of said tank in a direction opposite to said first direction.

2. Heat exchanger apparatus, comprising: a liquid tank; rnain duct means extending through said tank, said main duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank; fluid-moving means connected With said main duct means so as to urge fluid through the latter; and return duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said fluid over the exterior of said tank.

3. Heat exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank, said main duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank, the total cross-sectional area of said leg portions being less than that of said entrance portion; fluidmoving means connected with said main duct means so as to urge fluid through the latter; and return duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct sai fluid over the exterior of said tank.

4. Heat exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank, said main duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank; fluid-moving means connected with the inlet end of said main duct means so as to urge fluid through the latter in a first direction; return duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said fluid over the exterior of said tank in a direction opposite to said first direction; means having an inlet proximate said entrance portion for removing liquid from said tank; and means having a discharge opposite said entrance portion for returning liquid to said tank, the major portion of said liquid flowing through said tank in the second direction.

5. Heat exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank, said main duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank, the total cross-sectional area of said leg portions being less than that of said entrance portion; fluid-moving means connected With the inlet end of said main duct means so as to urge fluid through the latter in a first direction; return duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said fluid over the exterior of said tank in a direction opposite to said first direction; means having an inlet proximate said entrance portion for removing liquid from said tank; and means having a discharge opposite said entrance portion for returning liquid to said tank, the major portion of said liquid flowing through said tank in the second direction.

6. Heat exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank in heat-transfer relationship with the liquid contents of said tank; blower means having a discharge in communication with the inlet of said main duct means so as to urge fluid through the latter; mounting means interposed between said tank and said blower, said mounting means permitting the spacing of said blower relative to the inlet of said main duct means to be varied; and return duct means in communication with said main duct means, said return duct means being curved so as to direct said fluid over the exterior of said tank.

7. Heat exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank in heat-transfer relationship with the liquid contents of said tank; blower means having a discharge in communication with the inlet of said main duct means so as to urge fluid through the latter in a first direction; mounting means interposed between said tank and said blower, said mounting means permitting the spacing of said blower relative to the inlet of said main duct means to be varied; return duct means in communication with said main duct means, said return duct means being curved so as to direct said fluid over the exterior of said tank;

liquidremovingmeans disposed proximate the inlet end of said main ductmeans; and means disposed at the end of'saidtank remote from the inlet end of said main duct for returning liquid to i said tank means whereby the major'porti'on of liquid will flow through a tank in said 'se'cond direction opposite to said first direction.

8. Heat exchanger apparatus, comprising: a liquid tankymain duct means extending through said tank, said main duct'rneansincluding an entrance portion adjacent one end of said tank and a plurality of leg portions connecting saidentrance portion with the opposite end of said tank;'blower means having a discharge in communication with said entrance-portion so as to urge fluid throughsaidmain duct means in a first direction; mounting'means interposed between said tank and said blower, said'mounting means providing adjustment of the spacing between said entrance'portion and the discharge of said blower; and returnduct means including a plurality of diffuser members each being connected to one of said leg portionsadjac'ent said opposite end of said tank and being curved so as to direct said fluid over the exterior of said tank in a second direction opposite to said first direction.

9. Heat exchanger apparatus, comprising: a liquid tank; main'duct means extending through said tank, said main duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank, thetot'al cross-sectional area of said leg portions being less than that of-said entrance portion; blower means having a discharge in communication with said entrance portion so as to urgefiuid through said main duct means in a first direction; mounting means interposed between said tarikand :said blower, said mounting means providing adjustment of the spacing between said entrance portion and the'dischargeof said blower; and return'duct means including a plurality ofdifiuser members each being connected-toone of said leg portions adjacent said opposite end of said tank and being curved so as to direct said fluid over the exterior of said tank in a second direction opposite tosaid first direction.

IOFI-Ie'at exchanger apparatus, comprising: a liquid tank; main duct means extending through said tank, said main duct means'including an entrance portion adjacent one end of-said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank; blower means having a discharge in communication with said entrance portion so as to urge fluid through said m'ainduct meansin a first direction; mounting means interposed between said tank and said blower, said mounting means providing adjustment of the spacing between said entrance portion and'the discharge of said blower; return duct means'including a'plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct saidfluid over the-exterior of said tank in a direction opposite tosaid firs-t direction; means having an inlet proximate saidentrance portionfor removing liquid from said tank; and rneans'having a discharge opposite said entrance portion for =returning'liquid to said tank, the major portion of said liquid flowing through said tank in the second direction.

ll. Heat exchanger apparatus, comprising: a liquid tank;'mainduct means extending through said tank, said main duct means including an entrance portion adjacent one end of-said tank and a plurality of leg portions connectingsaid entrance portion with the opposite end of said tank, the total cross-sectional area of said leg portions being less than that of said entrance portion; blower means "having a discharge in communication with said entrance portion so as to urge fluid through said main duct means in a first direction; mounting means interposed between :said tank and said blower, said mounting means providing-adjustment of the spacing between said entrance portion and the discharge of said blower; return duct means including a-plurality of diffuser memberseach being connected to one ofsaidleg portions adjaceht said opposite end of said tank and beingcurved soas to-dire'ct said fluid over the exterior otsaidtzinkina directionopposite to said firstdirect'ion; means having an inlet proximate said entrance-portion for removing liquid fronrsaid =tank;'and means having a discharge opposite saiden'tran'ceportion for returning liquid 'to said tank, the-major portion of said liquid flowing through said tank in the second-direction.

12. 'Heat exchan'ger'apparatus, comprising: a horizontally extending liquid tank; main duct means extending through said tank, said main ductmeans including an entrance portion adjacent one end of said tank and aipairiof leg portions connecting said entrance portion'with the opposite end of said tank; blower means having a discharge in communication with said entrance portion so as to urge fluid-therethrough in a'first direction; return duct means including a pair of difluser members-each being connected to one of said leg portions adjacentsaid'opposite end of said tank and being curved so as to direct said fluid over the opposite external sides of saidtank-in a second direction opposite to said first direction; afloor'interconnecting the lower portions of'said leg portions, said floor terminating at a point remote from said opposite end of said tank; an upstanding bathe on said floor .atits point of termination and having a height approximately that of said leg portions; liquid withdrawal means in said tank adjacent said entrance portion;- and liquid return means including a discharge nozzle between said leg portions adjacent said opposite end .ofsaid tank and extend ing away from said opposite end so asto direct the major portion of liquid carried'therebyin said second direction.

-13. Heat exchanger apparatus as set forth in claim 12 wherein the combined vertical cross-sectional area of the leg portions of sa'id'm'ain duct'meansis lessthan that of the entrance portionthereof.

14. Heat exchanger apparatus, comprising: .a horizontally extending liquid tank; main :ductmeans extending through said tank, said' main duct means including an'entrance portion adjacent one end'of said tank andapair of leg portions connecting said entrance portion with the opposite end ofsaid tank; blower means having a discharge in communication with said entrance portion "so as to-urge fluid through said main duct means in a first direction; mounting means interposed between said tank 'andsaid blower, said mounting means providing adjustment of the spacing between said entrance portion and the discharge of said blower; return duct' means including-a pairof diffuser members, each being connected to one of said deg portions adjacent said opposite end of said tank andbeing curved so as to'direct said fluidover 'the opposite external sides of said tank in a second direction opposite to said first direction; a floor interconnecting the lower portions of said leg portions, said floor terminating at a point remote from said-opposite end of saidtank; an upstanding battle on said floor at its point of termination and having a height approximately that of said leg .portions; liquid withdrawal means in said tank adjacent said entrance portion; and liquid return means including a discharge nozzle between said leg portions adjacent said opposite-end ofsaid tank-and extending away from'said opposite end so as to direct the major portion of liquid carried thereby in said second direction.

15. Heat exchanger apparatus as set forth in claim 14 wherein the combined vertical cross-sectional area of the leg portions of said main duct means is less than that of the entrance portion thereof.

16. Heat exchanger apparatus, comprising: a liquid tank; main air duct means extending through said tank, said main air duct means including an entrance portion adjacent one end of said tank and a plurality of :leg portions .connectingsaid entrance portion with the opposite end of said tank; a blower connected with said main duct means so as to urgeair through the-latter; and'return air duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said air over the exterior of said tank.

17. Heat exchanger apparatus, comprising: a liquid tank; main air duct means extending through said tank, said main air duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank, the total cross-sectional area of said leg portions being less than that of said entrance portion; a blower connected with said main air duct means so as to urge air through the latter; and return air duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said air over the exterior of said tank.

18. Heat exchanger apparatus, comprising: a liquid tank; main air duct means extending through said tank, said main air duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank; a blower connected with the inlet end of said main air duct means so as to urge air through the latter in a first direction; return air duct means including a plurality of diifuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said air over the exterior of said tank in a direction opposite to said first direction; means having an inlet proximate said entrance portion for removing liquid from said tank;

and means having a discharge opposite said entrance portion for returning liquid to said tank, the major portion of said liquid flowing through said tank in the second direction.

19. Heat exchanger apparatus, comprising: a liquid tank; main air duct means extending through said tank, said main air duct means including an entrance portion adjacent one end of said tank and a plurality of leg portions connecting said entrance portion with the opposite end of said tank, the total cross-sectional area of said leg portions being less than that of said entrance portion; a blower connected with the inlet end of said main air duct means so as to urge air through the latter in a first direction; return air duct means including a plurality of diffuser members each being connected to one of said leg portions adjacent said opposite end of said tank and being curved so as to direct said air over the exterior of said tank in a direction opposite to said first direction; means having an inlet proximate said entrance portion for removing liquid from said tank; and means having a discharge opposite said entrance portion for returning liquid to said tank, the major portion of said liquid flowing through said tank in the second direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,109,064 Gettelman Feb. 22, 1938 FOREIGN PATENTS 86,263 Switzerland Aug. 16, 1920 

